The present invention relates to a method and apparatus for terminal connections for highly tensioned tubular elements in offshore applications. More particularly, the present invention relates to a method and system for flexibly connecting in a restrained termination pressurized, highly tensioned tubular elements extending from subsea facilities to compliant structures.
Traditional bottom-founded platforms having fixed or rigid tower structures have been taken to their logical depth limits in the development of offshore oil and gas reserves. Economic considerations suggest that alternatives to this traditional technology be used in the development of deepwater prospects.
Alternative designs have been developed for various configurations of "compliant structures", e.g. tension leg platforms, compliant towers, articulated towers and floating production facilities, which can support offshore developments in very deep water more economically than traditional fixed platforms. Further, a promising area being investigated among compliant structures is the use of minimal structures. Examples include tension leg well jackets and spar structures ranging form those providing completion and workover facilities through mini-spars and to riser buoys. All of these compliant structures are designed to "give" in a controlled manner in response to dynamic environmental loads rather than rigidly resist those forces. This results in relative motion between a foundation, template or other subsea facility and the topside facilities of the compliant structure.
Various components connect the subsea and topside facilities, including tubular elements such as production risers, export risers and tendons. These connections require a high degree of angular flexibility. However, accommodating this angular freedom with tubular goods in applications which must maintain continuous, hard-piped bores is a difficult challenge for traditional materials capable of meeting the rigorous pressure and tension requirements.
Various stress joint arrangements have been devised to help meet this challenge. Nevertheless, this remains a limiting factor in the design of compliant structures and offshore facilities. Thus there is a need for an improved system and method for providing flexibility to a restrained termination of highly pressurized, highly tensioned tubular elements in such offshore applications.